Fix stack vn_open()

We should not put a 4k maxpathlen buffer on the stack, instead
locate it to the heap.  Even in user space we run ztest with 8K
stacks to verify correctness

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index 4bd08cd..0559347 100644 (file)
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -517,10 +517,12 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
        int fd;
        vnode_t *vp;
        int old_umask;
-       char realpath[MAXPATHLEN];
+       char *realpath;
        struct stat64 st;
        int err;
 
+       realpath = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
+
        /*
         * If we're accessing a real disk from userland, we need to use
         * the character interface to avoid caching.  This is particularly
@@ -534,11 +536,16 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
        if (strncmp(path, "/dev/", 5) == 0) {
                char *dsk;
                fd = open64(path, O_RDONLY);
-               if (fd == -1)
-                       return (errno);
+               if (fd == -1) {
+                       err = errno;
+                       free(realpath);
+                       return (err);
+               }
                if (fstat64(fd, &st) == -1) {
+                       err = errno;
                        close(fd);
-                       return (errno);
+                       free(realpath);
+                       return (err);
                }
                close(fd);
                (void) sprintf(realpath, "%s", path);
@@ -548,8 +555,11 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
                            dsk + 1);
        } else {
                (void) sprintf(realpath, "%s", path);
-               if (!(flags & FCREAT) && stat64(realpath, &st) == -1)
-                       return (errno);
+               if (!(flags & FCREAT) && stat64(realpath, &st) == -1) {
+                       err = errno;
+                       free(realpath);
+                       return (err);
+               }
        }
 
        if (flags & FCREAT)
@@ -560,6 +570,7 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
         * FREAD and FWRITE to the corresponding O_RDONLY, O_WRONLY, and O_RDWR.
         */
        fd = open64(realpath, flags - FREAD, mode);
+       free(realpath);
 
        if (flags & FCREAT)
                (void) umask(old_umask);